The present invention relates to an injection molding die of an injection molding machine for the production of injection molded pieces made up of several plastic components, and for the production of hollow injection molded pieces, the die having a die base and an injection aperture, a sleeve element axially displaceable in the die base with a conical orifice and a closing pin or needle protruding into the sleeve element.
Austrian patent 342,287 discloses a method for the production of a shaped part by injection molding where two different plastic materials are injected from two cylinders into a common mold, so that an injection molded piece is obtained which comprises an outer layer and a core material. Here the die is designed as a two-way valve and is switchable in such a way that plastic material can be injected into the molding tool (die) either from one or from the other injection cylinder.
Similar methods are described in British patents 1,219,097 and 1,332,883.
German patent application OS 2,342,789 discloses an apparatus for intermittent production of multi-layer shaped bodies in which there are provided in the die base, an axially displaceable sleeve and inside the sleeve, an axially displaceable closing pin. By means of this apparatus, injection molded pieces consisting of different plastic components can also be produced.
German patent application OS 2,445,112, too, shows an injection molding die which is connected to three plasticizing cylinders and which has displaceable sleeves which alternately clear or shut off a die channel.
It is also known to inject a gas, generally nitrogen, into the mold during the injection molding process, in order thus to create an injection molded piece with cavities, whereby plastic material can be saved.